4 files changed, 283 insertions, 0 deletions
diff --git a/src/Platform/OpenGL/OpenGLFramebuffer.cpp b/src/Platform/OpenGL/OpenGLFramebuffer.cpp
new file mode 100644
index 0000000..523d748
--- /dev/null
+++ b/src/Platform/OpenGL/OpenGLFramebuffer.cpp
@@ -0,0 +1,238 @@
+#include "OpenGLFramebuffer.h"
+#include "Core/Log.h"
+
+#include <glad/glad.h>
+
+namespace Donut
+{
+    namespace Utils
+    {
+        static GLenum TextureTarget(bool multisampled)
+        {
+            return multisampled ? GL_TEXTURE_2D_MULTISAMPLE : GL_TEXTURE_2D;
+        }
+
+        static void BindTexture(bool multisampled, uint32_t id)
+        {
+            glBindTexture(TextureTarget(multisampled), id);
+        }
+
+        static void CreateTextures(bool multisampled, uint32_t* outID, uint32_t count)
+        {
+            glCreateTextures(TextureTarget(multisampled), count, outID);
+        }
+
+        static void AttachColorTexture(uint32_t id, int samples, GLenum internalFormat, GLenum format, uint32_t width, uint32_t height, int index)
+        {
+            bool multisampled = samples > 1;
+            if (multisampled)
+            {
+                glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, internalFormat, width, height, GL_FALSE);
+            }
+            else
+            {
+                glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, width, height, 0, format, GL_UNSIGNED_BYTE, nullptr);
+
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+            }
+
+            glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + index, TextureTarget(multisampled), id, 0);
+        }
+
+        static void AttachDepthTexture(uint32_t id, int samples, GLenum format, GLenum attachmentType, uint32_t width, uint32_t height)
+        {
+            bool multisampled = samples > 1;
+            if (multisampled)
+            {
+                glTexImage2DMultisample(GL_TEXTURE_2D_MULTISAMPLE, samples, format, width, height, GL_FALSE);
+            }
+            else
+            {
+                glTexStorage2D(GL_TEXTURE_2D, 1, format, width, height);
+
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+                glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+            }
+
+            glFramebufferTexture2D(GL_FRAMEBUFFER, attachmentType, TextureTarget(multisampled), id, 0);
+        }
+
+        static bool IsDepthFormat(FramebufferTextureFormat format)
+        {
+            switch (format)
+            {
+                case FramebufferTextureFormat::DEPTH24STENCIL8:  return true;
+            }
+            return false;
+        }
+
+        static GLenum DonutFBTextureFormatToGL(FramebufferTextureFormat format)
+        {
+            switch (format)
+            {
+                case FramebufferTextureFormat::RGBA8:       return GL_RGBA8;
+                case FramebufferTextureFormat::RED_INTEGER: return GL_RED_INTEGER;
+            }
+
+            return 0;
+        }
+    }
+
+    OpenGLFramebuffer::OpenGLFramebuffer(const FramebufferSpecification& spec)
+        : m_Specification(spec)
+    {
+        for (auto spec : m_Specification.Attachments.Attachments)
+        {
+            if (!Utils::IsDepthFormat(spec.TextureFormat))
+                m_ColorAttachmentSpecifications.emplace_back(spec);
+            else
+                m_DepthAttachmentSpecification = spec;
+        }
+
+        Invalidate();
+    }
+
+    OpenGLFramebuffer::~OpenGLFramebuffer()
+    {
+        glDeleteFramebuffers(1, &m_RendererID);
+        glDeleteTextures(static_cast<GLsizei>(m_ColorAttachments.size()), m_ColorAttachments.data());
+        glDeleteTextures(1, &m_DepthAttachment);
+    }
+
+    void OpenGLFramebuffer::Invalidate()
+    {
+        if (m_RendererID)
+        {
+            glDeleteFramebuffers(1, &m_RendererID);
+            glDeleteTextures(static_cast<GLsizei>(m_ColorAttachments.size()), m_ColorAttachments.data());
+            glDeleteTextures(1, &m_DepthAttachment);
+
+            m_ColorAttachments.clear();
+            m_DepthAttachment = 0;
+        }
+
+        glCreateFramebuffers(1, &m_RendererID);
+        glBindFramebuffer(GL_FRAMEBUFFER, m_RendererID);
+
+        bool multisample = m_Specification.Samples > 1;
+
+        // Attachments
+        if (m_ColorAttachmentSpecifications.size())
+        {
+            m_ColorAttachments.resize(m_ColorAttachmentSpecifications.size());
+            Utils::CreateTextures(multisample, m_ColorAttachments.data(), static_cast<uint32_t>(m_ColorAttachments.size()));
+
+            for (size_t i = 0; i < m_ColorAttachments.size(); i++)
+            {
+                Utils::BindTexture(multisample, m_ColorAttachments[i]);
+                switch (m_ColorAttachmentSpecifications[i].TextureFormat)
+                {
+                    case FramebufferTextureFormat::RGBA8:
+                        Utils::AttachColorTexture(m_ColorAttachments[i], m_Specification.Samples, GL_RGBA8, GL_RGBA, m_Specification.Width, m_Specification.Height, static_cast<int>(i));
+                        break;
+                    case FramebufferTextureFormat::RED_INTEGER:
+                        Utils::AttachColorTexture(m_ColorAttachments[i], m_Specification.Samples, GL_R32I, GL_RED_INTEGER, m_Specification.Width, m_Specification.Height, static_cast<int>(i));
+                        break;
+                }
+            }
+        }
+
+        if (m_DepthAttachmentSpecification.TextureFormat != FramebufferTextureFormat::None)
+        {
+            Utils::CreateTextures(multisample, &m_DepthAttachment, 1);
+            Utils::BindTexture(multisample, m_DepthAttachment);
+            switch (m_DepthAttachmentSpecification.TextureFormat)
+            {
+                case FramebufferTextureFormat::DEPTH24STENCIL8:
+                    Utils::AttachDepthTexture(m_DepthAttachment, m_Specification.Samples, GL_DEPTH24_STENCIL8, GL_DEPTH_STENCIL_ATTACHMENT, m_Specification.Width, m_Specification.Height);
+                    break;
+            }
+        }
+
+        if (m_ColorAttachments.size() > 1)
+        {
+            GLenum buffers[4] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1, GL_COLOR_ATTACHMENT2, GL_COLOR_ATTACHMENT3 };
+            glDrawBuffers(static_cast<GLsizei>(m_ColorAttachments.size()), buffers);
+        }
+        else if (m_ColorAttachments.empty())
+            glDrawBuffer(GL_NONE);
+
+        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
+        {
+            GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
+            switch (status)
+            {
+                case GL_FRAMEBUFFER_UNDEFINED:
+                    DONUT_ERROR("Framebuffer is undefined");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT:
+                    DONUT_ERROR("Framebuffer has incomplete attachment");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT:
+                    DONUT_ERROR("Framebuffer is missing attachment");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_DRAW_BUFFER:
+                    DONUT_ERROR("Framebuffer has incomplete draw buffer");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_READ_BUFFER:
+                    DONUT_ERROR("Framebuffer has incomplete read buffer");
+                    break;
+                case GL_FRAMEBUFFER_UNSUPPORTED:
+                    DONUT_ERROR("Framebuffer format is unsupported");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_MULTISAMPLE:
+                    DONUT_ERROR("Framebuffer has incomplete multisample");
+                    break;
+                case GL_FRAMEBUFFER_INCOMPLETE_LAYER_TARGETS:
+                    DONUT_ERROR("Framebuffer has incomplete layer targets");
+                    break;
+                default:
+                    DONUT_ERROR("Framebuffer is incomplete (unknown error: {})", status);
+                    break;
+            }
+        }
+
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+
+    void OpenGLFramebuffer::Bind()
+    {
+        glBindFramebuffer(GL_FRAMEBUFFER, m_RendererID);
+        glViewport(0, 0, m_Specification.Width, m_Specification.Height);
+    }
+
+    void OpenGLFramebuffer::Unbind()
+    {
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+
+    void OpenGLFramebuffer::Resize(uint32_t width, uint32_t height)
+    {
+        m_Specification.Width = width;
+        m_Specification.Height = height;
+
+        Invalidate();
+    }
+
+    int OpenGLFramebuffer::ReadPixel(uint32_t attachmentIndex, int x, int y)
+    {
+        glReadBuffer(GL_COLOR_ATTACHMENT0 + attachmentIndex);
+        int pixelData;
+        glReadPixels(x, y, 1, 1, GL_RED_INTEGER, GL_INT, &pixelData);
+        return pixelData;
+    }
+
+    void OpenGLFramebuffer::ClearAttachment(uint32_t attachmentIndex, int value)
+    {
+        auto& spec = m_ColorAttachmentSpecifications[attachmentIndex];
+        glClearTexImage(m_ColorAttachments[attachmentIndex], 0,
+            Utils::DonutFBTextureFormatToGL(spec.TextureFormat), GL_INT, &value);
+    }
+};
diff --git a/src/Platform/OpenGL/OpenGLFramebuffer.h b/src/Platform/OpenGL/OpenGLFramebuffer.h
new file mode 100644
index 0000000..8cd376c
--- /dev/null
+++ b/src/Platform/OpenGL/OpenGLFramebuffer.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include "Rendering/Framebuffer.h"
+
+namespace Donut
+{
+    class OpenGLFramebuffer : public Framebuffer
+    {
+    public:
+        OpenGLFramebuffer(const FramebufferSpecification& spec);
+        virtual ~OpenGLFramebuffer();
+
+        void Invalidate();
+
+        virtual void Bind()   override;
+        virtual void Unbind() override;
+
+        virtual void Resize(uint32_t width, uint32_t height)          override;
+        virtual int ReadPixel(uint32_t attachmentIndex, int x, int y) override;
+
+        virtual void ClearAttachment(uint32_t attachmentIndex, int value) override;
+        virtual uint32_t GetColorAttachmentRendererID(uint32_t index = 0) const override { return m_ColorAttachments[index]; }
+
+        virtual const FramebufferSpecification& GetSpecification() const override { return m_Specification; }
+    private:
+        uint32_t m_RendererID = 0;
+        FramebufferSpecification m_Specification;
+
+        std::vector<FramebufferTextureSpecification> m_ColorAttachmentSpecifications;
+        FramebufferTextureSpecification m_DepthAttachmentSpecification = FramebufferTextureFormat::None;
+
+        std::vector<uint32_t> m_ColorAttachments;
+        uint32_t m_DepthAttachment = 0;
+    };
+};
diff --git a/src/Platform/OpenGL/OpenGLRendererAPI.cpp b/src/Platform/OpenGL/OpenGLRendererAPI.cpp
index cd54f82..230b19b 100644
--- a/src/Platform/OpenGL/OpenGLRendererAPI.cpp
+++ b/src/Platform/OpenGL/OpenGLRendererAPI.cpp
@@ -106,4 +106,10 @@ namespace Donut
         glBindImageTexture(slot, textureID, 0, GL_FALSE, 0, 
                           readOnly ? GL_READ_ONLY : GL_WRITE_ONLY, GL_RGBA8);
     }
+
+    void OpenGLRendererAPI::ReadPixels(uint32_t x, uint32_t y, uint32_t width, uint32_t height, 
+                                       uint32_t format, uint32_t type, void* pixels)
+    {
+        glReadPixels(x, y, width, height, format, type, pixels);
+    }
 };
diff --git a/src/Platform/OpenGL/OpenGLRendererAPI.h b/src/Platform/OpenGL/OpenGLRendererAPI.h
index 0576db8..5a68622 100644
--- a/src/Platform/OpenGL/OpenGLRendererAPI.h
+++ b/src/Platform/OpenGL/OpenGLRendererAPI.h
@@ -36,5 +36,9 @@ namespace Donut
         virtual void BindImageTexture(uint32_t textureID, 
                                       uint32_t slot = 0, 
                                       bool readOnly = false)      override;
+        virtual void ReadPixels(uint32_t x, uint32_t y, 
+                                uint32_t width,  uint32_t height, 
+                                uint32_t format, uint32_t type, 
+                                void* pixels)                     override;
     };
 };